The field of the present invention relates to ballistic launch of a payload. In particular, multifunction aerodynamic housings are disclosed herein for ballistic launching of a payload.
A need exists for launching payloads into space. Examples of such payloads can include: satellites or other space vehicles; equipment, supplies, provisions, or fuel for spacecraft or space stations; projectile or explosive weaponry; or human or animal remains (usually cremated) or material for space burial or other purposes. Currently available launch technology relies almost exclusively on the use of ground-launched powered rockets for the first and all subsequent phases of launch and flight. The use of rockets has a number of disadvantages, which can include relatively high cost, lengthy launch preparations, long turnaround time between successive launches, or sensitivity to weather conditions at the launch site (because the slowest, and therefore most vulnerable, portions of the rocket's flight occur near the ground just after liftoff).
There have been a number of research efforts to develop a gun-launch alternative for launching payloads into space. Potential advantages of gun launching can include relatively lower cost, shorter launch preparations, relatively rapid turnaround between successive launches, or relative insensitivity to weather conditions at the launch site (because the fastest, and therefore least vulnerable, portions of the launched projectile's flight occurs as it exits the barrel of the gun, so that ground-level weather has a lesser effect on the flight).
Previous efforts to develop a gun-launch system for launching payloads into space include the High Altitude Research Program (HARP) in the 1960's and the Super High Altitude Research Program (SHARP) in the late 1980's and early 1990's; both of those were research programs of the United States government. During the course of HARP a 185 lb. rocket body was launched at a muzzle velocity of 2,160 m/s (7,100 ft/s or about Mach 6), reaching an altitude of about 180 kilometers (591,000 ft). A 5 kg projectile was launched at a muzzle velocity of 3,000 m/s (6,700 mph or about Mach 9) during the course of SHARP. Both projects were eventually cancelled.
Strictly ballistic flight following launch (i.e., without further propulsion after leaving the gun barrel) will not achieve a stable orbit. To achieve a stable earth orbit, additional, guided propulsion is required, typically a rocket motor or other on-board propulsion and guidance system incorporated into the projectile. One example is disclosed in the paper of Gilreath et al (“The Feasibility of Launching Small Satellites with a Light Gas Gun”; 12th AIAA/USU Conference on Small Satellites, Paper No. SSC98-III-6; 1998), which is attached as an Appendix and is hereby also incorporated by reference. Typically the on-board propulsion (e.g., a rocket motor) would not fire until after an initial period of strictly ballistic flight after launch from the gun barrel. At an appropriate point in the ballistic flight, the rocket motor can be fired to achieve orbital insertion. In contrast, if only sub-orbital flight is needed or desired, on-board propulsion and guidance of the projectile may not be needed; strictly ballistic flight could be sufficient in some instances. Likewise, if escape velocity is needed or desired without orbital insertion, then on-board propulsion and guidance may not be required if the muzzle velocity of the gun launch is sufficiently large (i.e., if the muzzle velocity exceeds escape velocity by a margin sufficient to allow for aerodynamic drag on the projectile during its flight). If the muzzle velocity is not large enough, on-board propulsion can be employed to achieve escape velocity.
The initial, ballistic portion of the projectile's flight, after being launched from the gun, is substantially determined by elevation and azimuth of the gun barrel, the muzzle velocity, aerodynamic drag on the projectile, and wind conditions. Typically, the projectile follows a generally parabolic, hyperbolic, or elliptical trajectory. Without additional, onboard propulsion, the projectile either reaches an apogee and falls back to earth, or escapes earth's gravitation altogether (if the muzzle velocity, reduced by aerodynamic drag, exceeds escape velocity). If orbital insertion is desired, or if muzzle velocity alone is insufficient to escape earth's gravity, then additional, onboard propulsion typically is required and can be implemented in a variety of ways.
One problem to address in achieving a gun-based space launch is overcoming aerodynamic drag encountered by the launched projectile, particularly at high Mach number in denser portions of the earth's atmosphere. Earlier attempts typically have not employed projectiles shaped to provide maximal reduction of aerodynamic drag. For example, the projectiles disclosed in the Gilreath paper were roughly conical (i.e., tapered in only the forward direction), which is not optimal for reducing aerodynamic drag. Although some rockets have a modest taper at the rear, such tapers are generally truncated to allow a large opening for the rocket exhaust, thereby increasing aerodynamic drag. A projectile tapered in both fore and aft directions nearly to a sharp point (i.e., bi-tapered or streamlined) is expected to result in relatively less aerodynamic drag (e.g., as shown in FIG. 1). Some examples suitable for super- or hyper-sonic flight are disclosed in the NASA Technical Report of Stivers et al (“Studies of optimum body shapes at hypersonic speeds”; NASA Technical Note D-4191; 1967), which is attached as an Appendix and is hereby also incorporated by reference; such examples can include a Sears-Haack profile, a parabolic arc profile, a Miele profile, or a Von Karman profile.
Further, a rocket motor suitable for use for orbital insertion or achieving escape velocity may not necessarily have an aerodynamic profile suitable for sustained super- or hyper-sonic flight, particularly in lower, denser regions of the earth's atmosphere. In systems that include a rocket motor for providing guidance or propulsion during later stages of flight, that rocket motor can introduce undesirable or unacceptable aerodynamic drag.